The average battery life of the iPhone 4S is reported to be 6.0 hours. Assume th

Question

The average battery life of the iPhone 4S is reported to be 6.0 hours. Assume that the standard deviation for the battery life for this cell phone is 48 minutes. A random sample of 42 iPhones had an average battery life of 5.86 hours. Which of the following statements is correct? The interval that contains 95% of the sample means is 5.09 and 5.80 hours. Because the sample mean is not between these two values, we do not have support that the average battery life equals 6.0 hours. The interval that contains 95% of the sample means is 5.76 and 6.24 hours. Because the sample mean is betveen these two values, we have suppot that the average batery lle eq 60 hours The interval that contains 95% of the sample means is 6.0 and 6.5 hours. Because the sample mean is not between these two values, we do not have support that the average battery life equals 6.0 hours. between these two values, we have support that the average battery life equals 6.0 hours

Explanation / Answer

x' = 5.86 = 6.0 = 48/60 = 0.8 z = 1.96 n = 42

Let the confidence interval be (a,b).

We have a = - z / n = 6.0 - 1.96*0.8 / 42 = 5.76

b = - z / n = 6.0 + 1.96*0.8 / 42 = 6.24.

The correct answer is the second option.

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